The present invention relates to a device and method for intraocular delivery of therapeutic agents. Preferred devices of the invention include a non-linear portion that resides within a patient""s eye during use that can facilitate the delivery of a therapeutic agent.
The delivery of drugs to the eye presents many challenges. The ocular absorption of systemically administered pharmacologic agents is limited by the blood ocular barrier, namely the tight junctions of the retinal pigment epithelium and vascular endothelial cells. High systemic doses can penetrate this blood ocular barrier in relatively small amounts, but expose the patient to the risk of systemic toxicity. Topical delivery of drugs often results in limited ocular absorption due to the complex hydrophobic/hydrophilic properties of the cornea and sclera. Additionally, topical agents are mechanically removed by the blink mechanism such that only approximately 15% of a single drop is absorbed. Diffusion of topically administered drugs to the posterior chamber occurs, but often at sub-therapeutic levels. Intravitreal injection of drugs is an effective means of delivering a drug to the posterior segment in high concentrations. However, these repeated intraocular injections carry the risk of infection, hemorrhage and retinal detachment. Patients also find this procedure somewhat difficult to endure.
Local sustained delivery of therapeutics to the posterior chamber is critical in managing several chronic diseases of the eye. To address this need, several drug delivery devices have been developed for intraocular insertion into the vitreous region of the eye.
U.S. Pat. No. 4,300,557, for example, describes an intraocular implant in the form of a silicone capsule, which can be filled with a drug to be delivered. The implant is inserted through an incision into the vitreous region of the eye. After insertion of the implant, the incision is closed and the capsule remains in place for a period of time. Attached to the implant is a tube that passes through the surface of the eye. The tube may be used for subsequent injection of a drug while the implant is in the eye. The implant may be removed by making a second surgical incision into the eye and retrieving the implant. While in the vitreous, the device is not anchored and may move about freely. Because the overall shape of the capsule is linear, the amount of drug that may held by the device and that may be delivered over the surface area of the device is limited. If the width of the capsule is increased, excessive sized incisions will be required for insertion of the device. If the length of the capsule is increased to greater than 1 cm, the implant will pass into the central visual field of the eye, thereby causing blind spots in the patient""s eye as well as increase risk of damage to the retinal tissue and lens capsule.
U.S. Pat. No. 5,378,475 describes a device which has been developed for insertion in the vitreous region of the eye, and is described in T. J. Smith et al., Sustained-Release Ganciclovir, Arch. Ophthalmol, 110, 255-258 (1992) and G. E. Sanborn, et al., Sustained-Release Ganciclovir Therapy for Treatment of Cytomegalovirus Retinitis. Use of an Intravitreal Device, Arch. Ophthalmol, 110, 188-195 (1992). This device consists of an inner core of pharmacologic agent surrounded by two coatings with different permeabilities. Drug diffuses through a small opening in one of these coatings achieving near-order release kinetics. It is implanted in the region of the pars plana through a 3.5-5.0 mm scleral incision. The implant must be removed and replaced every 6 months in the operating room as the drug becomes depleted. There is an approximately 25% complication rate from these procedures. The device is membrane diffusion drug delivery system that relies on EVA/PVA polymers to mediate release rate. Thus, many agents cannot be effectively delivered from such a system because their permeation rate through the rate controlling material of the system is too small to produce a useful effect. Other agents cannot be satisfactorily delivered by diffusional devices because of a particular chemical characteristic of the agent. This includes salts, because of their ionic character, and unstable polar compounds that cannot be formulated into a composition suitable for storage and delivery from such systems.
U.S. Pat. No. 5,098,443 describes certain specific implants that are inserted through incisions made in the eye wall or sutured around the globe of the eye. These rings may be formed from biodegradable polymers containing microparticles of drug. Alternatively, the implant may be in the form of a hollow flexible polymeric cocoon with the drug disposed therewithin for slow release by osmosis. No anchoring device is described.
U.S. Pat. No. 5,466,233 describes a certain tack for intraocular drug delivery. This device has an end that is positioned in the vitreous cavity while the head remains external to the eye and abuts the scleral surface. The tack contains a fixation portion to attempt to retain attachment within the eye. Because the overall shape of the capsule is linear, the amount of drug that may held by the device and the surface area through which the drug may be delivered is limited. If the width of the capsule is increased, excessive sized incisions will be required for insertion of the device. If the length of the capsule is increased to greater than 1 cm, the implant will pass into the central visual field of the eye, thereby causing blind spots in the patient""s eyes well as increase risk of damage to the retinal tissue and lens capsule.
The present invention provides methods and devices for the intraocular delivery of substances including, for example, therapeutic agents and medicaments.
Preferred devices of the invention have a non-linear shape during residence within a patient""s eye. Preferred designs have multiple turns or angles, particularly substantially coil or helical configurations, at least for those portions that reside within a patient""s eye during use.
Preferred device of the invention also include those that have a quite small cross-section shape, at least with respect to areas that reside within a patient""s eye during use. Such devices can be implanted by minimally invasive surgical procedures, including without the need for any sutures to implant or after use of the use.
An exemplary embodiment of the delivery device includes a body member that is non-linear in shape. In one embodiment, the device has a non-linear shape before, during and after the device is inserted into the eye. In another embodiment, the device is fabricated of a xe2x80x9cshape memoryxe2x80x9d material wherein the device is linear as it is inserted into the eye and wherein the device takes on a non-linear shape once it is implanted in the eye. Preferred shape memory materials include known materials such as, for example, shape memory alloys (SMA) like nitinol, shape memory polymers (SMP) like AB-polymer networks based on oligo(e-caprolactone) dimethacrylates and n-butyl acrylate.
We have found the non-linear shape of the body member provides a number of advantages. The non-linear shape provides a built-in anchoring mechanism that prevents unwanted movement of the device and unwanted ejection of the device out of the eye since the non-linear shape of the body member requires manipulation of the device to get it out of an incision. For example, in a preferred embodiment, wherein the implant is in the shape of a coil, the device can be removed only by twisting the device out of the eye and, thus, is not susceptible to ejection by the eye or unwanted movement within the eye. Further, the non-linear shape geometry of the body member provides greater surface area per length of the device. This is advantageous because it is desirable to limit the length of drug delivery implants to prevent the implant from entering the central visual field (See FIG. 6 which follows). If the implant enters the central visual field, this will result in blind spots in the patient""s vision and will increase the risk of damage to the retina tissue and lens capsule. By forming the body member in a non-linear shape, the device of the present invention holds a greater volume of materials per length of the device and it also provides a larger surface area per length of the device through which the material may be delivered.
The delivery device may further include a rim or cap at its proximal end. During use, the device is inserted into the eye through an incision until the rim or cap abuts the incision. If desired, the rim or cap may then be sutured to the eye to further stabilize and prevent the device from moving once it is implanted in its desired location.
In one embodiment, body member has a lumen extending along its length for housing the substance to be delivered. Preferably, a port in fluid communication with the lumen is located at the proximal end of the device. This allows for filling and refilling of the device after the device has been implanted in the eye. The substance in the lumen can then be delivered to the eye by a delivery mechanism. The lumen, in some embodiments, may further include a number of dividers to form a plurality of compartments each of which could be filled with a different substance, thereby allowing for delivery of more that one substances by the same device at the same time, if desired.
In one embodiment, the delivery mechanism comprises one or more exit apertures located at the distal end of the body member. In another embodiment, the delivery mechanism comprises a plurality of openings along the body member. In another embodiment, the delivery mechanism comprises the material forming the body member. For example, the material forming the body member may be a material that is permeable or semi-permeable to the substance to be delivered. In another embodiment, the body member is fabricated of a synthetic biodegradable polymer containing microparticles of the substance to be delivered. As the polymer decomposes, the substance to be delivered is released into the eye.
Other aspects and embodiments of the invention are discussed infra.